Support triangle interpolation

[tomrijnbeek]

🆙 Improvement proposal

#221 introduces interpolation based on 2 (in 1D) and 4 points (in 2D). We should also add interpolation methods to interpolating between 3 points (in 2D).

Context

While interpolating along a square grid is not uncommon, there are also use cases to be found for interpolating between 3 points. Specifically, interpolation between 3 points allows you to interpolate every point in a hexagonal grid. In turn, this can be used to generate noise maps based on a hexagonal grid instead of a square grid.

[tomrijnbeek]

Note that the recommended way to support this is by using barycentric coordinates in the triangle. This feature may have to come paired with some functions that make it easy to transform between different coordinate systems inside a triangle.